I have been the guest of Indian friends or relatives of friends for most of these first weeks of my journey. Now, in Manali, I meet fellow westerners. Suzie, blond, slimly elegant and British, founded Blazing Trails Tours in Goa some 18 years ago; Manali is the summer base from where she sends guided biker groups out to explore the lesser-known and most adventurous paths of Ladakh.

Rob, also English, and his local partner Roop Katoch, have been organising treks and fishing and cultural tours from Manali for 20 years. Three Texan retirees have adjoining apartments 10 minutes' walk up a mountainside; they met as members of a Buddhist meditation group in Austin more than 40 years ago.

Roddy is a tall, tough, enthusiastic Australian; he brought heli-skiing to Manali and is a self-taught engineer. He has designed a vehicle that can scale mountains and cross swamps and snowfields. He collects me in a standard Jeep. We zigzag up a pine-clad mountain to a hydro project, pass beyond barriers and signs forbidding photography and halt at a small parking lot above a foaming torrent.

An alpine meadow aglow with wild flowers rises steeply towards a crest of tall pines. A brown cow chews grass some 200m up the meadow. Roddy's prototype sits in a slight dip beyond the cow. It is a small Suzuki Jeep. Rather than wheels, it has four outsize rollers. The rollers are about a metre high, half a metre wide, well over a metre long and covered in a wiry green matting. The matting is sewn together with twine over a thick pad of pliable white honeycomb. The steering wheel has been replaced by two small levers in a box bolted to the floor between the driver's feet.

Roddy lifts the hood, clambers on to the engine and sucks accumulated rainwater out of the plugholes. The engine coughs a few times and fires unenthusiastically before settling. I take the passenger seat. Roddy turns the Jeep uphill and heads for a near-vertical section below the pines. I imagine the twine tearing loose, the Jeep rocketing down the mountain and the safety belt broken. Roddy grins happily as I cling to the hand grip on the dashboard. We are now on the steepest incline. I expect the Jeep to tumble backwards. My knuckles are white and I'm sweating. Roddy shuts down the engine.

"Thirty five degrees, he says as he consults a inclinometer. Satisfied, he clambers out and locks the doors. The rollers have flattened rather than crushed the grass and wild flowers; 48 hours and the tracks will have disappeared. I'm impressed.

Roddy notices my leather walking shoes and shows concern for the first time. Be careful on the way down. Don't slip. It's steep."